The Influence of Crystalline Admixtures on the Properties and Microstructure of Mortar Containing By-Products

Abstract

Crystalline admixtures and industrial by-products can be used in cement-based materials in order to improve their mechanical properties. The research examined long-term curing and the exposure to environmental actions of polymer–cement mortars with crystalline admixture (CA) and different by-products, including Bengħisa fly ash and Globigerina limestone waste filler. The by-products were introduced as a percentage replacement of the cement. A crystallization additive was also added to the mixtures in order to monitor the improvement in durability properties. The mechanical properties of the mortar were assessed, with 20% replacement of cement with fly ash resulting in the highest compressive strength after 540 days. The performance was analyzed with respect to various properties including permeable porosity, capillary suction, rapid chloride ion penetration and chloride migration coefficient. It was noted that the addition of fly ash and crystalline admixture significantly reduced the chloride ion penetration into the structure of the polymer cement mortar, resulting in improved durability. A microstructure investigation was conducted on the samples through Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS). Crystals forming through the crystalline admixture in the porous structure of the material were clearly observed, contributing to the improved properties of the cement-based polymer mortar.

Influence of Crystalline Admixtures and Their Synergetic Combinations with Other Constituents on Autonomous Healing in Cracked Concrete—A Review

“…As per recent studies [6,8,28,36,38,41,42,45,48,62,63], the needle-like healing products were characterized as ettringite crystals (AFt, 3CaO•Al 2 O 3 •3CaSO 4 •32H 2 O) through microstructural investigations. However, some microstructural studies reported non-ettringite needle-like products.…”

Geochemistry, Mineralogy and Textural Properties of the Lower Globigerina Limestone Used in the Built Heritage

“…LGL obtained from demolitions was often recycled for same uses. Today, it is utilized in polymer cement mortar [37,38] and reconstituted masonry products as an alternative to natural limestone and concrete blocks [39].…”

“…remarkable for its softness; it is worked easily, but it is not strong enough against moistures and the sea-breeze" [4] (pp. [37][38][39].…”

Salt Scaling Resistance of Variable w/c Ratio Air-Entrained Concretes Modified with Polycarboxylates as a Proper Consequence of Air Void System

“…The aspect of ensuring durability is the dominant factor of concretes produced today [ 18 , 24 , 25 , 26 , 27 , 28 ]. However, the current commonly used modifications of concrete compositions with admixtures [ 28 ], additives [ 18 , 27 ], modern calcium sulfoaluminate cement [ 26 ], or geopolymer [ 24 , 25 ] binders significantly change the structure of the concrete.…”

“…The aspect of ensuring durability is the dominant factor of concretes produced today [ 18 , 24 , 25 , 26 , 27 , 28 ]. However, the current commonly used modifications of concrete compositions with admixtures [ 28 ], additives [ 18 , 27 ], modern calcium sulfoaluminate cement [ 26 ], or geopolymer [ 24 , 25 ] binders significantly change the structure of the concrete. Consequently, the values of the air void parameters (AVPs) in hardened concrete, L ≤ 0.200 mm and micro air content (A 300 ) ≥ 1.8%, determined on the basis of the Powers model [ 6 , 7 , 9 ], do not always guarantee concrete frost resistance, especially in the case of surface interaction with defrosting agents, as is shown in the literature [ 1 , 3 , 4 , 7 , 29 , 30 , 31 , 32 ] and the author’s own research [ 33 , 34 ] on concrete produced today.…”